Backyard Aquaponics
A place to discuss aquaponics

Hello everyone,

I'm new to the forum and created my account because I'm experiencing some fish issues that i don't understand.

My system is the standard one GB IBC system demonstrated on this website. I've been cycling for 7 weeks now, haven't had any nitrites or nitrates yet, still waiting. I started my system with urine and some meat to provide ammonia. At 3 weeks, I decided to go ahead and introduce 50 tilapia fry, even though I had read I could expect to lose many of them until the system is cycled. About a week and a half later, all but 4 or 5 had died. Right before the 6 week mark I went ahead and got 80 more tilapia fry, thinking I could expect to lose some but that soon my system should be cycled.

After about a week and a half, most of them have again died, and I still have no nitrates. Here's my specs and water readings:

Ammonia: 0.25
PH: Has remained between 7 and 8, when it has exceed 8, I've done a 15-20% fresh water switch.
Nitrites and Nitrates: 0
Pump- 900 liter/hr
Water temp- 18-19 celsius

Some other important details:

-Fish don't seem to eat well, I'm getting build-up of fish feed on the bottom of the tank
-I've had two algael blooms. However, I read that tilapia will eat the algea, and my guys seemed to be eating the algea on the side of the tank.
-I was concerned about the cool water temp, so sometimes I added heated water, and later bought a metal heater to put in there for short periods (around an hour-two hours). The fish seemed to really like it, they would gather around it!

Now, I've been looking at the fish. Before dying, many of them started swimming lethargically, some hanging out around the surface, and others almost laying on the bottom until they died. I also noticed what appeared to be bubbles on their skin, and reddish mouths. Any ideas?

I was concerned before about the water temp, but I live in Kenya and the waterways around me (rivers and lakes) are filled with tilapia!

Any ideas on what's going on? My working theory is something called "gas bubble disease". Maybe the combination of the algea, heater and high output pump caused oversaturation?

HELP PLEASE!!

Add some salt to your system immediately, which will help your fish combat their sickness.

1kg salt per thousand litres of fish tank volume. Sea salt, or swimming pool salt, with no extra additives.

Remove the buildup of uneaten fish food off the bottom of the tank.

Are your fish getting enough oxygen? Is it possible to add an air pump/airstone to your fish tank, even temporarily whilst your fish recover?

And did you take any earlier tests on your water before adding fish? Even though your ammonia is low now, I suspect the fish are suffering the results of earlier Ammonia or Nitrite poisoning

Also what's the lowest temperature your water is getting down to?

What is your source of top up water and does it contain any chlorine?

I don't think this is the best way to lower your pH. It could be putting more shock on the fish, particularly if the pH is changing quickly with the water change

Hi Tigereye,

Sorry to hear your having troubles with the fish.

Might be a combination of things. Jono has some good suggestions.

Even though algae produces oxygen during the day, it consumes oxygen at night. I wouldn't be surprised if the oxygen levels are taking a nose dive overnight because of the algae blooms.

High pH means that it won't take much ammonia for it to be toxic to the fish. Take a look at the table in the back of the IBC's of Aquaponics (link in the upper right hand corner of your webpage).

The cool temps helps with the ammonia but the tilapia are probably stressed out a bit. Did you acclimate the fish to the water before putting them in?

Your basically doing close to one fish tank water change per hour. Lots of people have pumps the size of yours and no troubles. How is the water being added to the fish tank and how are you getting your aeration added?

Hope you get a handle on what's going on, keep plugging away

Hey guys,

Thanks for the quick responses. I'll answer the questions:

Jon:
-I'm limited on the salt types available. I'm out in the bush, would regular table salt work? If not, I'll need to look next time I go to Nairobi (the capital city, about two hours away).
-As for the fish feed, I'm removing as much of it as I can with a strainer, but the only way for me to remove it completely at this point would be to drain it.
-As for the oxygen, I'm not sure. I have a battery powered aerator I got in the event of power outages, but I don't have it running in the tank regularly. I thought the pump going at 900L/hr would be more than enough.
Then, it seemed like the issue might be too much oxygen, causing the "gas bubble disease" but I might be totally wrong.
-Ammonia levels were consistently .25 ppm before and after adding the fish.
-Lowest temp on the water has been 17.2 celsius.
-My top up water is from the local river, and the local water plant adds fluoride, no chlorine.

Scotty
-I got the fish from a dealer about 2 hours away, transported them home in an aerated plastic bag, and then set the bag in my tank for about 30 minutes before opening it up and letting them swim out. They seemed really lively for about a week, then got sluggish...
-The water is just a simple free fall from the grow bed. I'm running the pump 24/7, so its a constant flood system.

Any more ideas from the additional details? Again, thanks for helping with this, and taking the time to answer.

1. 17C if probably too low for the young ones. The supplier I use recommends 26C for blue tilapia fingerlings and they are more cold tolerant than others. Grow them in an indoor aquarium if heating is an issue. Once they are close to juvenile stage you can start reducing the water temp slowly to match your aquaponics temp before you move them.

2. DON'T mess with your pH. Most fish handle pH outside optimal ranges without issue. It's the fast changes that kill them.

3. Make-up water should be the same temp and pH of your system. Adding large quantities of different parameter water will kill your fish.

***YES! I do realize the irony of "KillerofFish" giving advice on keeping fish alive.

Thanks for the reply.

I think you're right, especially point two and three. Maybe this is just a case of too much change too frequently. Adding hot water to up the temp, switching out the water, using the heater, etc. It all must have been too much change too quickly.

Any other ideas?

Most table salts contain Iodine which would not be good for the fish. If you have plain salt, not iodised table salt, that would be ok.



No, don't drain the tank (will stress your fish even more). Can't you just manually siphon it out? Get an old hose and use it to siphon the gunk off the bottom of the tank (eg see this vid: http://www.youtube.com/watch?v=Z_lFtqsg6GY) Any hose will work as a siphon, you don't need the wider bit on the hose like in this vid. The wider diameter the hose the stronger the siphon will be.




Hard to say. How many fish do you have left? Can you post a photo of how you have your tanks setup? It would be good to rule out lack of oxygen as a factor in this puzzle of yours if at all possible.



No, I really don't think gas bubble disease is a concern here. Again, can you please post a photo of your tanks so we can advise better.




Just add the new water *slowly* to your tank so your fish can adjust to it. I wouldn't add any more than 20% top up water per day, to be safe. I'd do less than this ideally.



This would have adjusted your fish to temperature, but not the change in pH between their bagged water and your tank. Next time add a bit of the tank water into the bag every 5 mins or so over the course of about 30 mins, whilst floating the bag in the tank like you did. This will get your fish used to the temperature AND pH.



Usually fish exhibit a delayed response to a stressful event..

What is the pH of your top up water?

Wow, thanks for answering again Jono. I'll get some pics when I get home and respond again.

Thanks for the siphon idea with the hose, I don't know why I didn't think of that!

I'm having issues with the file size on the pics. Anyways, I siphoned the feed off the bottom, looks great now! The water is just a free fall from the GB to the FT.

I was looking as I was siphoning, I've got one lone survivor, seems as healthy as can be

I'm approaching 8 weeks, still no nitrites or nitrates...

Still can't get pictures up, but I did test the top up water. It's 6.6.

Yeh this forum has size limit on photos, they have to be less than 800 pixels wide which is smaller than the orignal images coming straight off your digital camera

You need to shrink them down using an image editing program (there are free ones available to download)

or if you were uploading the photos to facebook they will be the right size as facebook automatically resizes them

earthbound if you are reading this, it may be possible to integrate auto image resize php code into the forum

Well, I had the opportunity to get some more little guys today so I went ahead and got them!

When I got home, I siphoned the tank again and acclimated the fish to the water, first on temperature, then I started slowly adding the tank water to the bag to introduce them to it. My one survivor is still in there, and doing well! I did a full test on the water before I added them. Here are the results:

PH- 8
Ammonia- .25
Temp.- 19.2 C
Nitrites and Nitrates still zero

Any ideas on what my lack of nitrates issue is? I'm at 9 weeks and still haven't seen any!

Dissolved oxygen! Get some bubbles and some spray.

Cheers IanK (Tilapia are illegal in Australia! so I don't really know )

If your Ammonia isn't going up and you are feeding, then you are getting conversion. Lack of Nitrates is probably because they are being used up as fast as they are created. Before you mentioned algae, if you have plants or algae they will utilize the Nitrates, some of them don't even need to wait for the conversion process to occur. Algae can sometimes be a problem for this reason. Many people have no Nitrate but still get good plant growth so I'd take a look at how the plants are doing.